Quote:
Originally Posted by 1969 GMC
the cartridge filters dont have an anti-drainback valve because they are a full flow filter, not a bypass like most spin ons. some of the larger wix spin ons are full flow (I have the 2 qt. wix filter on my Ford, its a full flow design).
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All Chevrolet cartridge filters used on their V8's from 1956 thru 1969 were ALL full flow filters. 1970 and later spin-on's are also full flow filters. The reason anti-drainback valves were used on full flow filters whether spin on or cartridge is when they are mounted on an angle on the side of an engine, above the oil pan, oil would flow back down into the pan after the engine was stopped and would thus give an inaccurate oil level when checked. Whether or not a spin on or canister full flow filter has a anti-drainback valve depends on where the filter is mounted. THEY ARE NOT NEEDED ON CHEVYS.
Anti-drainback valves were never used on bypass oil filters. 99% of all bypass filters are cartridge type filters. Bypass oil filters are seldom seen anymore except on pre 1955 autos.